Jinghua Wu

Scalable synthesis of TiO2/graphene nanostructured composite with high-rate performance for lithium ion batteries.

A simple and scalable method is developed to synthesize TiO(2)/graphene nanostructured composites as high-performance anode materials for Li-ion batteries using hydroxyl titanium oxalate (HTO) as the intermediate for TiO(2). With assistance of a surfactant, amorphous HTO can condense as a flower-like nanostructure on graphene oxide (GO) sheets. By calcination, the HTO/GO nanocomposite can be converted to TiO(2)/graphene nanocomposite with well preserved flower-like nanostructure. In the composite, TiO(2) nanoparticles with an ultrasmall size of several nanometers construct the porous flower-like nanostructure which strongly attached onto conductive graphene nanosheets. The TiO(2)/graphene nanocomposite is able to deliver a capacity of 230 mA h g(-1) at 0.1 C (corresponding to a current density of 17 mA g(-1)), and demonstrates superior high-rate charge-discharge capability and cycling stability at charge/discharge rates up to 50 C in a half cell configuration. Full cell measurement using the TiO(2)/graphene as the anode material and spinel LiMnO(2) as the cathode material exhibit good high-rate performance and cycling stability, indicating that the TiO(2)/graphene nanocomposite has a practical application potential in advanced Li-ion batteries.

Effect of protein penetration into phospholipid monolayers: morphology and structure.

Abstract Phase transition and phase properties of dipalmitoylphosphatidylcholine (DPPC) monolayers penetrated by bovine β-lactoglobulin dissolved in a buffered aqueous subphase are experimentally studied. The phase transition during the penetration dynamics is indicated by a break point in the Π(t) transients. The condensed phase domains formed during the β-lactoglobulin penetration are visualized by Brewster angle microscopy (BAM). The lattice structure of the condensed phase is characterised by grazing incidence X-ray diffraction (GIXD). Experiments on the penetration kinetics of β-lactoglobulin into DPPC monolayers are performed, starting from different monolayer states and using different protein concentrations. The condensed phase formed after the main phase transition point, consists only of DPPC. The β-lactoglobulin penetration occurs without any specific interaction with the DPPC molecules. Number and growth of the domains depend on the area per DPPC molecule at which the β-lactoglobulin penetration takes place. A first-order main phase transition can be induced when the protein penetrates into a fluid (gaseous) DPPC monolayer. β-Lactoglobulin cannot penetrate into a condensed DPPC monolayer at a surface pressure above the equilibrium penetration pressure. Conformational changes and squeezing out of protein from the penetrated monolayer are studied by compression of penetrated monolayers in equilibrium.

The influence of high dielectric constant core on the activity of core–shell structure electrorheological fluid

The core-shell structural dielectric particles are applied widely in the electrorheological (ER) fluids. The properties of the dielectric core are critical factors influencing their ER activity. In this paper, we successfully synthesized two kinds of core-shell hydroxyl titanium oxalate (TOC) particles with SiO(2) and TiO(2) as core, respectively. The obtained core-shell structural SiO(2)-TOC and TiO(2)-TOC particles were well-dispersed spherical nanoparticles with ideal morphology and a narrow size distribution. Under DC electric fields, the TiO(2)-TOC ER fluid showed notable ER activity with a yield stress of about 96 kPa (at 4 kV/mm), which is 3 times of that SiO(2)-TOC ER fluid and outclassed the yield stress of the TOC ER fluid. The dielectric spectra indicated that the higher dielectric constant of TiO(2) core induces the stronger interaction between the neighboring particles, which contribute to the enhancement of ER activity.

Preparation of rod-like calcium titanyl oxalate with enhanced electrorheological activity and their morphological effect

Insufficient yield stress and electrorheological (ER) efficiency have already become the limitations for the practical application of ER fluids. Herein, we report a simple and scalable co-precipitation method for synthesizing surfactant-modified calcium titanyl oxalate (SCTO) particles with a rod-like structure. The obtained SCTO materials not only present a yield stress twice as that of granular CTO ER fluids but also demonstrate low zero-field viscosity, which results in a high ER efficiency. In terms of microstructure and dielectric analysis, we infer that the exceptional ER activity is in large part due the anisotropic morphology and improved wettability of the rod-like SCTO. This work provides the basis for the future development of ER fluids and the promotion of their practical application.

Fabrication of graphene oxide/Ag hybrids and their surface-enhanced Raman scattering characteristics

A kind of surface-enhanced Raman scattering (SERS) substrate with high sensitivity was prepared via covalent assembly between silver nanoparticles (AgNPs) and graphene oxide (GO) sheets. With the high specific surface area, GO sheets can adsorb plenty of AgNPs; moreover, these adsorbed AgNPs formed some gathered state which can generate more hot spots of SERS. 4-Mercaptopyridine (4-MPY) was used to evaluate the SERS performance of the as-prepared substrate. The Raman enhancement factor (EF) of 4-MPY on the GO/AgNPs hybrids was up to 5.04×10(7), and the detection limit was estimated to be as low as 1 nM. The result showed that GO/AgNPs hybrids can produce stronger signals compared to silver colloids.

Dynamic characterization of phospholipid/protein competitive adsorption at the aqueous solution/chloroform interface.

Abstract In the present paper, we use the drop volume method to study the dynamics of the competitive adsorption of the zwitterionic phospholipids (DPPC, DPPE, DMPC and DMPE) mixed with proteins (β-lactoglobulin, β-casein, and human serum albumin, respectively) at the chloroform/water interface. In order to investigate the main factors influencing the equilibrium interfacial tension of the mixed system (drops of lipid in chloroform formed in an aqueous protein solution environment), proteins of different conformation and concentration, and phospholipids of different structure have been investigated. It is observed that, with constant external protein concentration, the equilibrium interfacial tension γ decreases with the increase of internal lipid concentration. When the phospholipid concentration is close to the CAC, both the conformation and concentration of the protein do not influence the equilibrium interfacial tension of the mixed systems remarkably. With the same internal phase containing phospholipid in oil solvent and different external phases containing the protein in water, the γ– C isotherms show similar tendencies. Moreover, the structure of the phospholipid determines the equilibrium interfacial tension, where the lipid head group is much more significant rather than the chain length. The experimental results show that in DMPC-protein systems, the equilibrium interface tension decreases with the phospholipid concentration more rapidly than in DMPE-protein systems.

Formamide-modified titanium oxide nanoparticles with high electrorheological activity

TiOx-based nanospheres modified by formamide (FA) as dielectric particles for electrorheological (ER) fluids were successfully synthesized through simple sol–gel hydrolysis and self-assembly. The suspension containing TiOx–FA displays superior ER activity, with a yield stress of 148 kPa (at 5 kV mm−1) under a DC electric field, which is 10 times that of ER fluids containing pure TiOx nanoparticles. More importantly, comparison between the FA and N,N-dimethylformamide (DMF) as the shell structure indicated that the ER performance was positively correlated with the dielectric constant of the polar molecule shell. The result represents a critical step towards an in depth understanding the enhancement effect of polar molecules. This study can afford a new strategy to achieve optimal performance in ER fluids.

Influence of environmental characteristics and climatic factors on mites in the dust of air‐conditioner filters

UNLABELLED To investigate mites in the dust of air-conditioner filters (MACF) in China, a total of 652 dust samples were collected from six cities: Guangzhou (n = 129), Nanchang (n = 127), Shanghai (n = 113), Xian (n = 93), Beijing (n = 93), and Shenyang (n = 79). Tarsonemus granarius was the most dominant species (87.2%). Dermatophagoides pteronyssinus and Dermatophagoides farinae only represented 7.0 and 3.0% of total mites, respectively. With latitude increasing, both mite occurrence rate (P < 0.001) and density (mites/g dust) (P < 0.001) were significantly decreasing. Multivariate regression analysis suggested that the annual average temperature and minimum temperature in different cities had dominant influences on MACF density. The logistic regression analysis revealed that the presence of MACF was positively associated with air-conditioner age, utilization time and power. Wall and window type air-conditioner had higher risk of finding MACF than the floor type air-conditioner. As far as the cleaning interval time of ACF was concerned, higher risk ratio and the highest density of MACF were found in the time stage of >3, < or =12 months. It was also suggested that house type could influence the presence of MACF. A negative association between the house floor and the MACF prevalence was found as well. PRACTICAL IMPLICATIONS Mites present in the dust of air-conditioner filters are potential indoor threat to asthma and allergy sufferers. In this study, we find that the storage mite Tarsonemus granarius is the predominant species of mites in the dust of air-conditioner filters (MACF). Thus, the possible clinical importance of T. granarius should cause more our attentions in the future. The abundance and distribution of MACF are also found significantly varied in different climatic regions of China. When we try to assess the possible risk of MACF, more attentions should be focused on subtropical region than temperate region. The influence analysis of environmental characteristics on the prevalence of MACF will shed light on the establishment of mite control strategy and the design of mite defense air-conditioner.

Effect of dodecyl dimethyl phosphine oxide penetration into phospholipid monolayers: morphology and dynamics

Abstract The penetration kinetics of dodecyl dimethyl phosphine oxide (C 12 DMPO) into a Langmuir monolayer of dipalmitoylphosphatidylcholine (DPPC) and the corresponding morphology were experimentally studied. It was found that under proper conditions the penetration of dodecyl dimethyl phosphine oxide could induce a first-order phase transition in the fluid-like lipid Langmuir monolayer. The transition is indicated by a break point in the Π ( t ) penetration kinetics curves and can be visualized by BAM. The dynamics of the penetrated layer and the subphase effect on the Langmuir monolayer were also investigated. The experimental results show that the adsorption of soluble molecules increases the surface density, which in turn causes the first-order phase transition in the monolayer. When the surface density reaches a certain critical value, the main phase transition sets in.

Influence of volume fraction on the yield behavior of giant electrorheological fluid

In this letter, we provide a phenomenological model to explain the recently discovered volume fraction effect in giant electrorheological (ER) fluids. We attribute the exponential dependence of yield stress on volume fraction to the repulsive interaction between particle chains. The increase of particle concentration increases the inter-chain repulsive interaction, which raises potential energy in electrorheological fluid and consequently the yield stress. The acquired normal force data validated our model.